The present invention generally relates to an electrical connection box for connecting, through branching, wiring harnesses installed in a motor vehicle and more particularly, to a drainage construction for the electrical connection box, which is capable of easily and positively discharging water penetrating into the electrical connection box.
Usually, an electrical connection box such as a junction block, a relay block, etc. is formed by assembling a lower casing and an upper casing. In the electrical connection box, bus bars for branch connection are accommodated through insulation plates and tabs bent from the bus bars are projected from terminal through-holes formed on the lower casing or the upper casing so as to be connected to wiring harnesses.
Namely, as shown in FIGS. 1 and 2, a plurality of tabs 2 projecting from bus bars (not shown) are inserted from above through a plurality of terminal through-holes 1b formed on a bottom plate 1a of a lower casing 1 so as to be connected to connectors (not shown) provided at a distal end of a wiring harness. At this time, each of the terminal through-holes 1b is formed into a shape substantially identical with that of each of the tabs 2 as shown in FIG. 1 and the tab 2 is passed through the terminal through-hole 1b through its substantial contact with the terminal through-hole 1b so as to be closely held by the terminal through-hole 1b as shown in FIG. 2. Meanwhile, although not specifically shown, an upper cover is mounted on an upper portion of the upper casing, while a lower cover is mounted on a lower portion of the lower casing 1. The connectors to be connected to the bus bars are accommodated in the lower cover and the lower cover is formed with a drainage hole.
Such a phenomenon that water penetrates into the electrical connection box formed by the upper and lower casings may be caused by dropwise condensation or the like. In such a case, water drops reach the bottom plate 1a of the lower casing 1 via the tabs 2 as shown in FIG. 3. However, since there is substantially no gap between the tab 2 and the terminal through-hole 1b, water drops proceeding along the tabs 2 are spread on an upper face of the bottom plate 1a so as to bridge neighboring tabs 2 for electrical conduction therebetween as shown in FIG. 3. As a result, such a problem may arise that shortcircuiting occurs in the circuit, thereby resulting in malfunction of the circuit.